Contributing

The most valuable contribution is a new risk pattern — something pytest-mrt doesn't currently catch.

If you've been burned by a migration that caused a production incident, there's a good chance it should be in here.

Setup

git clone https://github.com/croc100/pytest-mrt
cd pytest-mrt
python3 -m venv .venv
source .venv/bin/activate
pip install -e ".[dev]"

Running tests

pytest tests/ -v

Adding a new risk pattern

1. Write a _check_* function in pytest_mrt/core/detector.py
2. Add it to the _CHECKS list at the bottom of that file
3. Write a positive test (pattern detected) and a negative test (clean migration not flagged) in tests/test_detector.py
4. Add the pattern to the table in docs/patterns.md

def _check_my_pattern(source: str, rev: str, fname: str) -> list[RiskWarning]:
    body = _upgrade_body(source)
    if re.search(r"some_pattern", body):
        return [RiskWarning(
            rev, fname,
            "Pattern name",
            "Human-readable explanation of why this is dangerous",
            "error",  # or "warning"
        )]
    return []

Commit style

feat: add detection for X pattern
fix: handle edge case in Y check
docs: update patterns page
test: add negative case for Z

Opening a PR

Use the PR template — it has a checklist to make sure nothing is missed.